The nature of many agricultural implements (especially for grain crops) is to have a series of devices (discs, shovels, row units, spray nozzles, etc.) that are spanned across a bar or boom that runs perpendicular to the axis of motion of the tractor or other vehicle. When the implement is used, the devices run at parallel intervals (which may or may not be evenly spaced) in relation to the direction of forward motion of the vehicle. If the devices are “active” (driven or controlled by external means to perform a function), they are usually controlled by one or more of the following methods: mechanical, hydraulic, pneumatic, or electronic. An example of an active device would be a planter row unit that dispenses seed from a seed storage container into a planted row in the ground. Planter row units may be controlled by one or a combination of the previously listed methods. Active-electromechanical devices are active devices that can be controlled electronically.
The devices on agricultural implements and vehicles may also be “passive”, which means they are sensors that detect one or more field conditions or implement/vehicle conditions. An example of a passive sensor is a soil probe which detects the pH level of the soil.
In the field of precision agriculture, passive devices are typically used to spatially record varying field or crop conditions. Active-electromechanical devices are used to variably apply some product (seed, fertilizer, or chemical) or perform some other function according to the device's location within the field. Spatial control of active-electromechanical devices is based on either currently sensed data or prescriptions, which associate spatial locations within the field with a particular rate (or other variable-level of device function). Prescriptions are often, but not always, based on previously sensed field conditions. A Global Positioning System (GPS) receiver is typically used to determine the implement/vehicle location within the field, which is used for the spatial data logging and control.
If the devices are controlled and/or communicate electronically, they may be connected to a common data bus that allows the devices to receive control and configuration data and transmit status and configuration data (this would typically be implemented with a Controller Area Network or CAN bus). Any device that is connected to the common data bus may transmit data to one or more devices connected to the bus and may receive data from any device connected to the bus. When an implement or vehicle is configured with multiple devices spanned across a bar or boom that perform some function, it is important that each device has a unique positional address so that its physical positioning can be determined by other modules in the system. Each electronic module also needs a unique address so that the other electronic modules can individually communicate with it. There are several methods for assigning unique positional addresses to multiple devices that are listed below:                1. Configurable jumpers or switches on the device to assign the address.        2. Devices must be plugged in one-at-a-time so either the device itself or some other controlling device can determine what address needs to be used and assign it.        3. Devices are wired in-order and communicate with an external controlling device (master module) when they receive an “assign address” signal such as disclosed in U.S. Pat. Nos. 5,809,440 and 5,635,911.        4. Configured address signal pins in the device connectors along the implement wiring harness that determine address based on where the device is connected in the harness.        
The problem with these methods is that they require special action on the device (from either an operator/technician or an external device) or a specially-designed wiring harness to assign an address so it functions properly. The method described in this invention assigns device addresses without the need for any special action. Each module is responsible for monitoring the shared data bus and assigning its own address when it receives the address assignment signal from the adjacent module.
Automatic address identification is important because devices and the wiring harnesses that connect them can be manufactured identically with no special process or programming needed to assign the device's address. Also, it means that any of the identical devices can be placed at any of the device positions without any need to reprogram or change the device address.
In some agricultural operations like liquid application, the use of multiple tiers of control has several advantages including larger range of control and faster response times to reach different rates. Tiers are items, like sprayer booms, that are located at nearly the same physical position and apply to the same physical area. If a system of active or passive devices on an agricultural vehicle or implement has more than one tier, the tier becomes part of the physical address of each device and must also be settable and determinable for each device. The method described in the present invention uses a tier input signal as part of the physical address to allow for two tiers to be used in a system.